This invention relates to the refining or upgrading of hydrocarbons containing arsenic, and is most particularly related to the removal or arsenic from hydrocarbon liquids, especially from shale oils or fractions derived therefrom.
Metals contained in crude oils, residual fractions, and the like present difficulties in refining or upgrading to more valuable products, such as gasoline, turbine fuel, etc. Most metals, for example, vanadium and nickel, and to lesser extent iron and copper, deactivate a variety of refining catalysts, and, as a result, processes generically termed "demetallization" or "demetallation" have been proposed for removing deleterious metals from hydrocarbons prior to the catalytic refining thereof. In some of these processes, the hydrocarbon contaminated with metals is treated with a sulfur-containing agent. For example, as disclosed in U.S. Pat. No. 2,683,683, sulfiding agents, such as hydrogen sulfide and ammonical hydrogen sulfide, are reacted with the heavy metal components of a hydrocarbon fraction to produce insoluble heavy metal sulfides, the sulfides then being removed by filtration, electrostatic separation, etc. In another process, described more fully in U.S. Pat. No. 2,854,399, heavy metals are removed by passage of the contaminated hydrocarbon through a bed of solid, elemental sulfur. And in yet another process, dilute sulfuric acid is employed, as disclosed in U.S. Pat. No. 2,778,777, to convert heavy metal constituents in a hydrocarbon to water-soluble forms which are then removed by washing with water.
In addition to vanadium, nickel, and other metals, it is often desirable to remove arsenic from hydrocarbons, particularly with respect to shale oils and fractions derived therefrom. Raw shale oil produced by retorting oil shale from the Green River area of Utah, Colorado, and Wyoming, which oil shale is often termed "Colorado oil shale," usually contains arsenic components in concentrations ranging between about 20 and 80 wppm (calculated as arsenic). In order to upgrade shale oils containing arsenic in such relatively large concentrations, it is a virtual necessity for the oil to be purified of arsenic, the deactivation effects of arsenic on many refining catalysts, especially hydrotreating catalysts, being well known. Accordingly, processes have been developed for removing arsenic from hydrocarbons, and particularly from shale oils and the like. An exemplary process, disclosed in U.S. Pat. No. 4,046,674, employs a catalytic absorbent for this purpose. In another process, disclosed in U.S. Pat. No. 4,075,085, arsenic is removed from hydrocarbons after heating in the presence of oil-soluble nickel, cobalt, or copper additives.
There is, therefore, an ongoing effort being made in the art to remove arsenic from shale oils and the like. Accordingly, it is an object of the present invention to provide a process for reducing the concentration of arsenic in shale oil and other arsenic-containing hydrocarbons. Other objects and advantages will appear to those skilled in the art from the following description of the invention.